Some current hybrid transmissions feature two electric motors coupled to an internal combustion engine by dual clutches and include gear sets coupled to the clutches and electric motors. Typical prior art transmissions arrange the electric motors, clutches and gear sets such that the actual torque applied by the electric motors and elsewhere within the transmission is significantly amplified at the transmission clutches. This higher torque requires larger, more durable clutches to be fitted into the transmission, increasing size, weight, and cost. Because typical prior art transmissions amplify the torque applied at the clutches, larger, more powerful electric motors are needed to provide enough torque to start an engine coupled to the transmission. Larger motors increase the cost and size of the transmission and create additional packaging difficulties. Thus, there remains a need for improvement in hybrid electrically variable transmissions.
Some typical prior art transmissions utilize two clutches coupled to the electric motors and gears within the transmission. Each clutch typically requires a dedicated bearing, increasing friction losses within the transmission and increasing costs. Thus, there remains a need for improvement in hybrid electrically variable transmissions.
In many typical prior art transmissions, a clutch disk is forced under pressure into contact with a friction plate to transfer power from a first set of components to a second set of components. The applied pressure is relieved when power is no longer to be transferred. However, the clutch disk and friction plate are still left to gently rub against one another causing friction losses, vibration, and wear. What is needed, therefore, is a clutch separator mechanism to prevent contact between the clutch disk and friction plate when the clutch assembly is deactivated. As the clutch disk and friction plate wear in typical prior art transmissions, the distance between the clutch disk and friction plate increases when in the deactivated state. As a result, greater movement and time is needed to fully activate the clutch assembly. In some circumstances, the clutch assembly may not be capable of sufficient movement to fully activate the clutch. Thus, there remains a need for improvement in hybrid electrically variable transmissions.